Now, a year and a half after joining Facebook, Gowalla's co-founder and former CEO Josh Williams is leaving.

Williams joined Facebook as a product manager where he worked on Pages, Location and Events. Gowalla launched before Foursquare in 2007 but only ever reached a few million downloads. Foursquare now has more than 30 million downloads and billions of check-ins, although it hasn't had a smooth ride either.

Williams, who moved from Austin, Texas to join Facebook in Palo Alto, says he'll remain in San Francisco to pursue a new project.

"No comment on my next steps at this point — beyond that I plan to stay in SF and work on something new," Williams told Business Insider. His last day is this Friday.

Williams and his co-founder were moved to join Facebook after attending the F8 conference in 2011. "We were blown away by Facebook’s new developments. A few weeks later Facebook called, and it became clear that the way for our team to have the biggest impact was to work together," Williams wrote when he announced the acquisition.

We reached out to Facebook about Williams' departure and are awaiting official comment.